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The basic product for Hamm roller
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The basic product for Hamm roller
Deskripsi lengkap
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This document will help you！
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project on mechanical seal.
2015
Roller #4 Seal Problem
Submitted by: Inspection Team Members
Under supervision: Eng. Ashraf Fahmi Preventive Maintenance Manger
March 24
M.Gamal [Type the company name] 2/5/2015
Table of content 1.Introduction
Page 3
2. Maintenance history
Page 3
3. Problem Description
Page 3
4. Problem Evaluation
Page 6
5. Bearings Check
Page 7
5-1. Visual inspection
Page 7
5-2. Roller Lubrication Oil Analysis
Page 9
6. Conclusion
Page 9
7. Recommendation
Page 9
Inspection Dept.
Page 2 of 10
1. Introduction We faced a technical problem at the latest overhauling for roller no.4, this report represent a clarification for this problem. We hope to help us by a technical support.
2. Maintenance history Before describe the problem I like to illustrate the maintenance history for roller no.4. At October 2012
The roller bearings have been replaced. The mechanical seal has been replaced.
At October 2013
The seal has been replaced due to leakage at the contact surface between the sealing cover and roller hub flange Fig2.1.
Fig 2.1 3. Problem Description During seal replacement at October.2013 we checked the distance between the thrust collar and the sealing cover X Fig 3.1 before dismantle the old seal and it was 18.00 mm. We started to erect the new seal following FULLER company instructions step by step, and everything was normal, until we measured the distances X, Y and W Fig3.1 to calculate Z, The results are listed in the table below Table 3.1.
Inspection Dept.
Page 3 of 10
Fi 3.1
Dimension
Position 0◦
Position 90◦
Position 180◦
Position 270◦
Average
W
21
21
21
21
21
l
X
18
18
18.7
18.7
18.35
r
Y
20
20
20
20
20
1 ia T
Z (Actual) = 21.00 + 18.35 + 20.00 = 59.35 mm W
21
21
21
21
21
l
X
18.3
18.15
18
18.2
18.1625
r
Y
20
20
20
20
20
2 ai T
Z (Actual) = 21.00 + 18.1625 + 20.00 = 59.1625 mm
Table 3.1 So, According to FULLER Company instructions the final value of Z is not accepted Fig3.2 and we need machining at surface A.
Fig 3.2 So we had a confusion which is how the old seal didn’t need any machining and the new one needs machining, In addition to we have replaced roller seals many times before and no one needed machining.
Inspection Dept.
Page 4 of 10
We decide to make an illogical action; it was rotating the roller shaft when the roller was seated on its end as shown at Fig3.3.
Fig 3.3 We repeated measurement and the result was a surprise, the results are listed i n the table below Table 3.2 .
1 l ai r T
Dimension
Position 0◦
Position 90◦
Position
Position
180◦
270◦
W
21
21
21
21
21
X
13.4
13.15
13.1
13.5
13.29
Y
20
20
20
20
20
Average
Z (Actual) = 21.00 + 13.29 + 20.00 = 54.29 mm
2 l ia r T
W
21
21
21
21
21
X
13.3
13.4
13.2
13.3
13.3
Y
20
20
20
20
20
Z (Actual) = 21.00 + 13.3 + 20.00 = 54.3 mm
Table 3.1 So, According to FULLER Company instructions, Z value is with in tolerance Fig 3.4.
Fig 3.4 According to the final result we proceed to erect the seal to the final step Inspection Dept.
Page 5 of 10
4. Problem Evaluation First let us assume that the distance X before rotating the roller shaft is X1 and after shaft rotating is X2 and for the old seal is X0. Returning to the roller assembly, we will find that the thrust collar is fixed with the roller shaft and the seal cover is fixed with the roller hub, So the difference between X1 and X2 represent axial clearance (axial play) at the assembly, appeared when the roller shaft –with the thrust cover-moved towards the sealing cover during rotation of the shaft Fig 4.1 Note:-
The rotation of the shaft is an important action when adjusting bearing preload to guarantee that the bearings are fully seated.
Fig 4.1 It supposes that there is no axial clearance at the assembly because the assembly is under preload, means an axial interference between rollers and raceways such that there is no measurable axial shaft movement when axial force is applied – in both directions – while oscillating or rotating the shaft.
If we have a looseness at the assembly (Axial End play) Fig 4.2, bearings will not be stiff enough to resist the axial load from grinding process which will cause bearings to fail. Actually bearings status until now is very good according to the regular check.
Fig 4.2 Inspection Dept.
Page 6 of 10
5. Bearings Check During raw mill operation from October 2013 until now many inspection programs has been executed as follows. 5.1 Visual inspection 1. At October 2013 shutdown
Bearings have been inspected visually and they are in good conditions Fig 5.1.
No existence for chips at roller housing and Supply filter enclosure.
Fig 5.1 2. At February 2014
Bearings have been inspected visually and they are in good conditions Fig 5.2.
No existence for chips at roller housing and Supply filter enclosure.
Fig 5.2 Inspection Dept.
Page 7 of 10
3. At October 2014
Bearings have been inspected visually and they are in good conditions Fig 5.3.
No existence for chips at roller housing and Supply filter enclosure.
Fig 5.3 1. At February 2015
Bearings have been inspected visually and they are in good conditions Fig 5.4.
No existence for chips at roller housing and Supply filter enclosure.
Fig 5.4
Inspection Dept.
Page 8 of 10
5.2 Roller Lubrication Oil Analysis
1. At January 2014
The oil sample has been analyzed by SHELL CO. and the result was as mentioned below: The amount of water contamination is too high. The spectrometry shows satisfactory wear levels for this equipment. Check and eliminate the source of the water contamination.
2. At November 2014
The oil sample has been analyzed by MANTRAC CO. and the result was as mentioned below: The Sample test results all indicate that the equipment/vehicle and lubricant are both performing within normal working limits.
3. At November 2014
The oil sample has been analyzed by SHELL CO. and the result was as mentioned below: The Sample test results all indicate that the equipment/vehicle and lubricant are both performing within normal working limits. Please continue normal operation and review again at the next scheduled sample.
Note:-
At February 2015 the roller has been checked for ships through the return line for the lubrication oil.
6. Conclusion 1. Theoretically the difference between X1 and X2 translated to axial play at the bearing assembly which conflict with engineering logic and reality since roller bearings are in good condition. 2. Fortunately the roller bearings until now are in good condition, so we can’t complete with this risk.
7. Recommendation 1. First of all we must prepare the spare roller, not only for this situation. 2. Measure the end play of the roller bearings after dismantling the roller to make sure that the bearing under preload or not. 3. According to the end play value the correction will be done:
End play = 0 No correction action needed.
Inspection Dept.
Page 9 of 10
End play > 0
Proposal A : replace the roller completely. Proposal B: it’s forbidden to make a preload for old bearing (used bearing) this matter is a recommendation from
Eng. Ahmed Salah bearing specialist SKF company, so we recommend adjusting the play to be zero or + (0.05 to 0.1) mm to reduce impact severity, and roller elements sliding motion. The ideal operating bearing setting is near zer o to maximize bearing life time; so we need bearings to be set with small endplay (yellow range) instead of high end play (red range) at the assembly to reach the desired near zero setting at operating temperature when mounted as a compromised solution. Fig 6.1
